In 1958 the United States made its initial steps towards the goal of manned space flight with Project Mercury. Seven men were selected to be the first American astronauts to test the limits of human endurance in space. Behind the scenes, there was a steep learning curve in the new science of astronautics. Testing astronaut candidates became a science in itself, as the effects of space travel on humans was still a mystery. Producers Judith Kampfner and Robin Wise talk to the scientists behind the Mercury Project, and to some of the men and women who trained to be among the first to leave the boundaries of earth.